Blocking-layer electrode system



SMOKING-LAYER ELECTRODE SYSTEM Filed Aug. 2s, 1945 TmRlYEY Paternal Dec. 21, 194s BLOCKING-LAYER ELECTRODE SYSTEM w Willem Christiaan van Geel, Eindhoven, Netherlands, assignor to Hartford National Trust Co., Hartford, Conn., as trustee Bank v&

Application August 28, 1945, Serial No. 613,153

VIn the Netherlands April 21, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires April 21, 1961 The invention relates to a blocking-layer electrode system comprising at least one grid embedded in the blocking layer.

With blocking layer cells of the above-mentioned type grid emission may occurv to a high extent. As is wellknown this drawback may be combatted by constituting the grid or the superficial layers thereof of semi-conductive or poorlyconducting material.

The invention has for its object to combat the drawback of grid emission still more efciently.

The present invention is based on the idea that grid emission is always liable to occur since the grid and the anode jointly form a blocking-layer electrode system wherein the grid performs the function of a cathode, for when a blocking-layer cell is used as an amplifier, a detector or a modulator the anode always has a positive potential with respect to the grid. Ii' the emissive capacity of the grid'exceeds that of the anode, the total of the forward current in the sytem grid-anode has to be taken into account.

The invention is based on the view that ii' in the system formed by the anode and the grid/'the latter has a poorer emissivity than the former/this system, considered as a rectier is utilized exclusively in the non-conductive direction, which involves that the current flowing in this system has avery low intensity. The feature of the invention is therefore that the emissive capacity of the grid material is at the most equal to that of the anode material.

If the conductivity of the grid material is exexample if they both consist oi' metal, there consequently occurs in this system no emission at all, for in order to obtain an electron current in a blocking-layer cell it is necessary that both electrodes should consist of materials having diierent emissive capacities. Also, however. if the grid material has a lower emissive capacity thanthe anode material the emission is of so low an order as to be negligible.

By carrying the rule according to the invention into effect we obtain a great liberty in the choice of the materials for theelectrodes, harmful grid emission being always avoided.

One particular embodiment is characterized, for example, in that the cathode consists oi' satis factorily emitting, semi-conductive material which has a higher emissivity than the anodeand grid-materials. If previously semi-conductors were utilized in locking-layer cells, they acted as anodes and for he latter use was made of substances having a actly equal to that of the anode material, for

`viously utilized semi-conductors,

event at comparatively `:acquires a relatively considerable value since at the emissive capacity of the grid equal to or lower 2 low emissive capacity. Since in the present case this semi-conductive material acts as a cathode. use is made here, in contradistinction to the preof a substance having a favourable emissive capacity. A ieW examples of satisfactorily emitting semi-,conductors are lead sulphide and copper sulphide. The specic resistance of these substances, which is a measure of the emissive capacity, amounts to 10*2 ohm-cm.

In this embodiment, wherein the cathode and the anode are both semi-conductors, the characteristic curve of the cathode-anode current is a 3/2-power curve. Systems having such a characteristic curve are extremely suitable for operation in the region of comparatively low anode voltages f since, even at low voltages, there owsa proportionally heavy emission current.

In this form of construction, for the cathodelanode current of the system use is still made of the satisfactoryemission of the cathode.

It maybe advantageous, however, to utilize a form of construction wherein the anode consists of satisfactorily emitting material, for example of metahthe cathode of a material having an appreciably lower emissive capacity and the grid of a material of equal or still lower emissivity.

In fact, if the anode consists of a metal the current-voltage characteristic curve` has in general the shape of an e-power curve, in which high voltages the current higher voltages the curve has a steep slope.

In this case, as in the case of the preceding form of construction, it is advantageous to take than that of the cathode since otherwise, considering the low emissivity of the cathode, there exists a particularly great danger of a gridcathode current being produced.

The expressions emissive capacity of the anode, cathode or grid material have, of course,y fundamentally to be understood in such manner that that supercial layer of the electrode which plays a part in the emission, that is to say the layr adjoining the blocking layer, is meant here. It is consequently possible to start for these electrodes, `for example, from a layer of satisfactorily conductive material both surfaces or one of the surfaces of which are converted into a layer of lower emissive capacity.

Starting from the principal idea of the invention that the emissive capacity of the grid material is lower or at the most equal to that ot the -anode material, it may occur that for the grid use is made of a material which has itself a higher emissivity than the cathode-material if the latter has a lower emissive capacity than the anode. It

would be-possible, for example, to start from metal for the anode and the grid. According to one advantageous embodiment of the invention,

' sirable grid-anode current while the'material on that portion of the grid directed vtowards the cathode is chosen to avoid undesirable gridcathode current.

An advantageous form of construction consists i in that the grid is constituted by a material which has a higher emissive capacity than the anode and cathode materials and whichexhibits on the anode side a covering layer whose emissive capacity is at the most equal to that of the anode material whilst on the cathode side there is also a by a layer ci chlorinated rubber lacquerapplied from a solution, to which layer selenium having a lower emissive capacity than the anode material is applied by vaporisation.- ASubsequently the second blocking lm, constituted by a layer of nitro-cellulose lacquer, is provided whereupon the cathode consisting of cuprous sulphide is formed.

The emissive capacities of the various electrodes are in this case such that the cathode has the highest emissive capacity, the anode has -a lower emissive capacity and the grid has the'lowest emissive capacity of all three.

4 Y Example Hl In the formation of an anode the starting point is formed by a copper plate which is superilcially converted, owing to the'action of iodine vapours, into cuprous iodide which is a' semi-conductor. On this layer is formed a blocking lm of Canada balsam to which is applied the grid consisting of selenium. To the latter lsapplied the second covering layer whose lemissive capacity isfhowever, at the most equa1 to that of the cathode material. In this case the starting point is consequently formed by a satisfactorily emitting and therefore satisfactorily conductive material for the grid.` This is advantageous, for, although no current may pass through the grid, the use of poorly conducting substances is undesirable since in this case such a grid follows with dilculty the applied voltage variations, the' drawbacks inherent in the use of a satisfactorily emitting grid material being nevertheless eliminated in the above-described manner.

The invention may be advantageously carried out with the use of one and the same starting material'for different electrodes whilst, depending on the character of the electrodes, this material is given different conductivities. As such may be utilized, for example, selenium which is known to have an emissive ,capacity which is liable to be varied within very wide limits.

There follow below a few practical examples of electrode systems according to the invention whilst, in addition,v the manner in which such systems may be manufactured, is brieily indicated.

Eamplel The starting point is formed by a silver plate 4which acts as a cathode and to which is applied from a solution a polystyrene layer having a thickness of about 5 microns and acting as a blocking illm. Then the grid is formed by ap'- plying selenium to which admixtures' are added in order to increase the conductivity of the selenium. The grid layer is coated with a second blocking layer, for example Canada balsam. The anode Example Il As the anode is utilized satisfactorily conducting selenium applied in the known manner to an .underlayeiz The rst blocking lm is constituted blocking film, which consists of chlorinated rubber lacquer, whereupon the cathode is formed,

which cathode consists of selenium which has a higher emissive capacity thanthe grid material but a lower emissive capacity than the anode material.

Example IV In this practical example the cathode consists of metalffor example copper, the first blocking lm lof polystyrene to which film-a layer of copper is applied by vaporisation. Owing to the action of iodine or sulphur. the separate copper'layer of the grid is converted into cuprous iodide or cuprous sulphide respectively. To the latter layer is applied the second blocking film of chlorinated rubber lacquer to which is applied the anode consisting of cuprous iodide. In this mode of realisation the anode hasv a lower emissive capacity than the cathode. That surface of the grid which is directed towards the anode has an emissive capacity which is equal to that of-the anode so that grid emission in the direction of the anode does not occur. On the other hand, the emissive capacity of that side of the grid which is directed towards the cathode is equal to that of the cathode, for this surface and the cathode consist both of copper, grid emission in the direction of Ythe cathode being consequently also excluded.

Without departing from the basic invention, other materials of lower or higher emissive capacities for the electrodes may be chosen. However, the mutual proportion of the emissive capacities of the electrodes must still be retained for an emcient blocking layer system.

As regards the construction-of the grid, it may furthermore be noted that the power of transmitting electrons travelling from cathode to anode is obtained, for example, owing to the fact that the grid layer is given an extremely slight thickness, for example of 1 micron. In the layer are producedv in this case extremely small holes l which impart thereto the properties of a grid.

The figure shows the construction of an electrode system according to the invention. I designates a supporting plateconsisting of copper, which carries a. layer 2 of cuprous iodide. On this layer bears a blocking iilm 3 consisting of Canada balsam. This lm carries in its yturn a grid layer 4 consisting of satisfactorily conducting selenium. The grid layer. bears a second blocking lm ilA which consists of chlorinated rubber lacquer. Finally there is present a. silver layer 6 applied by vaporisation. which layer constitutesv the cathode. The formation of this system is a that the electric eld between these two members is so slight that an electron current cannot be produced.

With the use of cuprous iodide and similar substances the conductivity can be adjusted. at will by ensuring that the material contains more or less free iodine.

Whatl claim is;

1. A blocking layer cell comprising cathode `and anode electrodes, a blocking layer between said electrodes, a control electrode embedded in said blocking layer and consisting of a material of which at least the lsurface portion thereof facing said anode electrode has an electron emissive capacity not greater than the emisslvity of the material comprising said anode electrode.

2. A blocking layer cell comprising anode and cathode electrodes, a blocking layer between said electrodes, a, control electrode embedded in said blocking layer and consisting of a material oiy which at least the surface portions thereof facing said anode and cathode electrodes have an electron emissive capacity not greater than the emissivities of the. materials comprising said anode and cathode electrodes.

` 3. A blocking layer cell comprising anode and cathode electrodes, said cathode electrode con# sisting of a material having a higher electron emissive capacity than the material comprising said anode electrode, a. blocking layer between said electrodes, and a grid electrode embedded in said blocking layer and consisting of a material having an electron emissive capacity not greater than the'emissivity of said anode material.

4. A blocking layer cell lcomprising anode and cathode electrodes, said anode electrode consisting oi a material having a higher electron emissivity than the material comprising said cathode electrode, a blocking layer between said electrodes, a grid electrode embedded in said blockf ing layer and consisting of a material oi which thesurface portion thereof facing the'anode electrode has an electron emissive capacity not greater than the emissivity of saidv anode material and the` surface portion thereof of said grid material facing said cathode electrode having an electron emissive capacity not greater than the emissivity of said cathode material.

s. A making layer een conipusingianod'e and cathode'electrodes, said cathode electrode con'- sisting of a material having a higher elel'stron` emissive capacity than the material comprising said anode electrode, a blocking layer between .said electrodes and a selenium grid embedded in said electrode. said selenium grid having an .electron emissive capacity not greater than the emissivlty oi said anode material.

.6. A blocking layer cell comprising anode and cathode electrodes, said anode electrode consisting of a material having a. higher electron emissive capacity than the emissivity oi the material comprising said cathode electrode, a blocking layer between said electrodes, a selenium grid embedded in said blocking layer, said selenium grid having an electron emissive capacity not greater than the emissivity of said anode material, and said selenium grid also having an electron emissive capacity not greater than emissivity of said cathode material.

'7. A blocking layer cell comprising a cathode electrode consisting of cuprous sulfide, an anode electrode consisting of selenium, said anode electrode having an electron emisisve capacity not greater than the emisisve capacity of said cathode electrode, a blocking layer between said electrodes,A and a selenium grid embedded in said blocking layer, said selenium grid having an electron emissive capacity not greater than the electron emissive capacity of said anode electrode.

.8. A blocking layer cell comprising a cathode electrode consisting of' selenium, an anode electrode of which at least that surface portion facing the cathode consists of cuprous iodide, said cathode electrode having an electron emissive capacity not greater than the electron emissive capacity of said anode electrode, and a blocking layer between said electrodes, a selenium grid embedded in said blocking layer,` said selenium grid having an electron .emissive capacity not greater than the emisslvity of said anode electrode, and said grid electrode also having an electron emissive capacity not greater than the emissivity of said cathode electrode.

9. A blocking layer cell comprising a cathode electrode consisting of copper, an anode electrode consisting of cuprous iodide, a blocking layerl between said electrodes, and a grid electrode embedded in said blocking layer, said grid electrode conslsting'of a layer of cuprous iodide on the side facing said anode electrode and a layer oi copper onV the side facing said cathode WILLEM CHRISTIAAN VAN GEEL.

BEFEREN CES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS electrode.

Great Britain Feb. 7, 1939 Great Britain Feb. "I, 1939 Number Esseling Aug. 31, 1943 

